I’m aware of two strains that are extremely low in CBD; AC/DC and Charlotte’s Web. AC/DC is a sativa strain with a CBD:THC ratio of 20:1 while Charlotte’s Web is a hybrid which has less than 0.3% THC! These strains were developed to help treat pain, anxiety, epilepsy, multiple sclerosis, and chemotherapy side effects without intoxication. Charlotte’s Web was created specifically for a young epileptic named Charlotte by Colorado growers and may be more difficult to find.
Remember that THC can have uplifting effects, so you might consider something with more THC that is still relatively low on the psychoactive scale, such as the sativa Harlequin. Harlequin has a 1:1 ratio of CBD:THC so may counteract depression while still maintaining cognition.